There's an outside chance the next Democratic debate could just be a face-off between Hillary Clinton and Bernie Sanders. NBC, the host of the next Democratic debate slated for Jan. 17, announced its criteria for candidates to make the stage Friday and, as it stands, former Maryland Gov. Martin O'Malley just barely makes the cut.

NBC's criteria requires that candidates have a polling average of 5 percent nationally or in Iowa, New Hampshire, or South Carolina, where the debate is being...